A light bulb uses 1.2 A when connected across a 120 V source. What power is used by the bulb?
Also, what current flows through a 75W bulb connected to a 120 V outlet?
thanks for any help with this question.
the power, P = I^2 * R = (V^2)/R
but what is R? we can find it using ohms law
V = IR
=> R = V/I = 120/1.2 = 100
=> P = (V^2)/R = (120^2)/100 = 144 watts
P = (V^2)/R
Also, what current flows through a 75W bulb connected to a 120 V outlet?
=> 75 = (120^2)/R
=> R = (120^2)/75 = 192 ohms
Now V = IR
=> I = V/R = 120/192 = 0.625 amps
or we could have found I directly, without first finding R:
P = (I^2)*R
since V = IR => R = V/I
so P= (I^2)(V/I) = IV
=> I = P/V = 75/120 = 0.625